The present disclosure relates to amplifying circuits including an active inductor.
Recently, various wireless communication services such as cellular telephones and wireless local area networks (LANs) have become available. In particular, attention is being given to multiband technologies which enable an apparatus to include a plurality of systems. Further, since battery-activated systems are used in the field related to the specified low power radio communication, there is an increasing demand for the systems to reduce power consumption in order to increase the lives of batteries.
Low noise amplifiers (LNAs) provided at the first stage in a large-scale integrated circuit (LSI) are key components for producing an apparatus capable of supporting multiple frequency bands. Conventionally, apparatuses capable of supporting multiple frequency bands have been produced by installing a plurality of LNAs each handling a corresponding frequency band or by installing a plurality of switchable inductors serving as LNA loads (see Win-Ming Chang et al., “2.45 GHz/5.2 GHz switched dual-band CMOS LNA with 4 gain control modes,” APMC 2005 Proceedings).
However, installing a plurality of LNAs or using a plurality of inductors each made of an interconnecting wire leads to an increase in the layout area, and accordingly, to an increase in costs of the LSI.
Under these circumstances, active inductors including a metal oxide semiconductor (MOS) transistor and a resistive element have been developed. Use of the active inductor as a load of an amplifier can reduce a layout area as compared to a case where inductors made of interconnecting wires are used (see U.S. Patent Publication No. 2008/0204171).